Reproduction of a new inferior vena cava thrombosis model and study of the evolutionary process of thrombolysis in rats

Objective To investigate the reproduction of a new model of thrombosis of inferior vena cava (IVC), and explore the natural process of thrombolysis and its mechanism in rats. Methods Forty-eight SD rats were randomly classified into experimental group and control group. In the experimental group, the lumen of the vena cava was blocked by about 80%-90% with a ligature of IVC below the left renal vein, and then the animals were redivided into three subgroups (n=12, each). In group A, the IVC endothelium was damaged and its tributaries were ligated. In group B, the IVC endothelium was damaged and its tributaries were not ligated. In group C, no damage was done to the endothelium of the IVC but all its tributaries were ligated. A sham-operated group served as control. The length and weight of the vinous thrombus and the percentage of the IVC luminal area were compared after operation to determine the optimum animal model of venous thrombosis. According to the best mode to establish the model, the thrombus specimens were collected and detected by HE and Masson staining, and the ED-1 expressions were examined by immunohistochemical staining after thrombus formation in 30 rats. The natural evolution of intravenous thrombolysis was analyzed dynamically and the cell types involved in this process were observed. Results Gross observation showed that the experimental group was successfully induced thrombus formation. The thrombus length and weight in group A was significantly higher than that in group B and group C, and no difference between group B and C. The thrombus area in group A was significantly higher than that in groups B and group C, which identified the group A was the optimal model group of venous thrombosis. In the group reproduced by the best mode of the model, HE and Masson staining results showed that new capillaries and the components of collagen and extracellular matrix increased gradually with the passage of time in the process of thrombus resolution. ED-1 staining indicated a massive infiltration with macrophages during the thrombus resolution. The results of inferior vena cavography showed that natural resolution of the IVC thrombus and complete revascularization needed 3 or 4 weeks. Conclusions The morphological changes in venous thrombus induced by narrow lumen combined with ligation and vessel injury of the IVC in rats are similar to those in human being, which could be a preferred method to establish animal model of deep venous thrombosis. The evolution of natural thrombus resolution comprises angiogenesis and the macrophages play an important role in this process.\n\t\t\n\t\tDOI: 10.11855/j.issn.0577-7402.2015.08.02